by John Logan in the April 2004 RootesReview
Our own Rootes Review Editor, Jim Anderson sent me this question: “One of the headlights on my Alpine was very dim. I changed the sealed beam unit. Still very dim. That suggests to me that there is a bad ground. What would be the logical place to start looking? I guess not the fuse box since both headlights are on the same circuit and the other headlight is fine. Any suggestions?”
Jim, you are lucky that only one headlight is dim because that helps in isolating the problem. The two major problems with Sunbeam wiring and in my opinion the reason why Lucas got the name “Prince of Darkness,” are poor grounds and those tube connectors. On each side of the hood opening about where the rubber hood bumper is, there is a bundle of those connectors and a black ground wire that completes the circuit to the rusty body under the hood bumper.
First, check all the connectors on the dim side by simply tugging on them and pushing them together. Some may have pulled out due to vibration. Rootes didn’t leave much slack in this part of the wiring harness.
If the light is still dim, check the black ground wire. The wire may be broken, the bumper may be loose, or the problem may be the body rust under the bumper. Remove the bumper, clean any rust on the body at the bumper, replace the connector if required and reinstall everything with a clean star washer.
If the light is still dim, the problem may be at the bulb. Since you have already replaced the bulb you probably would have noticed a problem with the three-prong plug but at this point I’m running out of suggestions. Remove the bulb again and check it. The connector may be bent or loose at the bulb or the ground wire into the connector may be failing.
If all these suggestions fail to fix the problem, then check for damaged wires or other loose connectors in the harness, especially the wires from the bundle of connectors to the lights.
Field Report: The solution worked like a charm, involving about 15 minutes of light labor. It turned out to be the black ground wire to the body under the hood bumper. I took the rubber bumper off, sanded the body where the ground connection is supposed to make the electrical connection, put on a new washer, tightened it up and everything works as new.
Resolution: Do the same for the other side before it also goes dim.